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|Authors:||Musmade, Ashok Mathaji|
|Title:||GENTIC STUDIES ON YIELD AND POWDERY MILDEW EESISTMCE IN CUCUMBER (Cncumis sativus L.)|
|Publisher:||MAHATMA PHULE KRISHI VIDYAPEETH RAHURI, 418 722 DIST.- AHMEDNAGAR, Maharashtra State (India)|
|Abstract:||An investigation was undertaken with a view to study the extent of heterosis, general and specific combining ability effects, heritability, gene action, genetic advance and degree of dominance for various economic characters and powdery mildew resistance in cucumber. Nine lines and six testerswere crossed using Line x Tester mating system. The resulting 54 F« hybrids alongwith parents were evaluated during 1987-89. The eleven best combinations selected on the basis of performance were further subjected to six generation(P1# P2# F]_# &2* B, and B2) analysis to study the nature and magnitude of gene action. Five most outstanding crosses were screened against the powdery mildew incidence. Significant and positive heterosis was observed for yield and its contributing characters. The percentage of heterotic crosses showing heterosis over better parent were maximum for yield per vine and diameter of fruit (61.11%) followed by fruit size index (55.56%), average weight of fruit (50.00%), earliness (44.44%), number of fruits per vine (42.59%), fruit length (37.04%) and days to first fruit picking (29.63%). While 27.78, 25.92 and 20.37 per cent crosses exhibited heterosis over better parent for nodal position of first female flower, flesh thickness and vine length. The percentage of heterosis for yield per vine ranged from -46.79 to 106.37. The most promising hybrids were L2 x T,- for earliness and days to first fruit picking. While hybrid Lg x T3, L~ x T^, L x T2 and L& x T for yield and other important characters. Besides high yield potential, shelf life of cucumber is an important character. The parent Lg (Sel.75»2-10) and T2 (Poinsette) recorded good keeping quality in terms of delayed bronzing of the fruits; incidently, the hybrid between these two parents also revealed very good shelf life of the fruits.The studies on combining ability revealed that the parents Pandhari Lamb Kakari (Lc), Sel.75-2-10 (Lg), Improved Long Green (Lg), Poinsette (T2) and Tokyo Summer (T-) exhibited good general combining ability for most of the characters. The maximumsea effects were recorded for yield, fruit weight and fruitsize index. The combination Lg x Tj recorded the highest seaeffects for yield and average fruit weight. Incidently, thiswas the most heterotic combinations for yield and other important characters. The estimates of sea effects were higher than gca effects indicating predominance of non-additive type of gene action for most of the characters. The situation^ therefore y indicated the possibility of commercial exploitation of hybrid vigour by using suitable combinations. The analysis of genetic variance and gene effects revealed that dominance variance played important role for most of the characters in some combinations; while, additive variance was also important in some combinations. All the three types of gene action (additive, dominance and epistatis) were present in most of the combinations for important characters. Complementary epistasis was observed in cross Lq x T_ for early fruit giqking *D txa fruit size index in hybrid L2 x T1 for number of fruits per vine and in cross Lg x T_ for average weight of fruit.The -Y\3flgg heritability estimates from 53-3 6. To l-5&-% was , recorded for fruit size index, nodal position of first female flower, average weight of fruit and numberof fruits per vine. The heritability estimates for yield per vine, vine length, flesh thickness and days to first fruit picking were medium (36. J6 to 4-6 -31 %)^ whereas^the estimates were low for diameter - (11 -J&., " . High genetic advance was observed for yield per vine and average weight of fruit* These observations suggestedthat the yield and their contributing characters couldbe improved through selection in segregating populations. The studies on inheritance of powdery mildew indicated The presence of epistasisjgene action. Duplicate type ofepistatis was observed in all the five cross combinations. The resistance to powdery mildew was controlled by recessivegene which indicated dominance of susceptibility.|
|Appears in Collections:||Thesis|
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